[Bug binutils/10288] "objdump -D --target=binary -m arm7tdmi" shows non-ARM7TDMI instructions

[chris at seberino dot org]

------- Additional Comments From chris at seberino dot org  2009-07-16 18:16 
-------
Nick

Many bit regions in ARM instructions are specified as SBZ "Should Be Zero".

ARM docs say if these bits are NOT zero that the results are UNPREDICTABLE for
all ARM chips!

So the question is what is the best thing for objdump to do in these situations
where a bit region is not zeroed out when it should be.

I think the cleanest thing to do is to return UNDEFINED.  I found some incorrect
ldrsb's and ldrsh's that I think would best be interpreted as UNDEFINED 
instead....

Here are some examples. (These all have SBZ regions that aren't zeroed out)...
<    2fe40:     001001d0        ldrsbeq r0, [r0], -r0
<    2fe44:     001001d1        ldrsbeq r0, [r0], -r1
<    2fe48:     001001d2        ldrsbeq r0, [r0], -r2
<    2fe4c:     001001d3        ldrsbeq r0, [r0], -r3
<    2fe50:     001001d4        ldrsbeq r0, [r0], -r4
<    2fe54:     001001d5        ldrsbeq r0, [r0], -r5
<    2fe58:     001001d6        ldrsbeq r0, [r0], -r6
<    2fe5c:     001001d7        ldrsbeq r0, [r0], -r7
<    2fe60:     001001d8        ldrsbeq r0, [r0], -r8
<    2fe64:     001001d9        ldrsbeq r0, [r0], -r9

<    2fec0:     001001f0        ldrsheq r0, [r0], -r0
<    2fec4:     001001f1        ldrsheq r0, [r0], -r1
<    2fec8:     001001f2        ldrsheq r0, [r0], -r2
<    2fecc:     001001f3        ldrsheq r0, [r0], -r3
<    2fed0:     001001f4        ldrsheq r0, [r0], -r4
<    2fed4:     001001f5        ldrsheq r0, [r0], -r5
<    2fed8:     001001f6        ldrsheq r0, [r0], -r6

...etc.

Would it be hard for you to make these return UNDEFINED?

cs


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http://sourceware.org/bugzilla/show_bug.cgi?id=10288

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